The present invention relates to a set square.
Set squares in general are well-known. The usual form is that of a right angled triangle whose other angles are both 45.degree. or are 60.degree. and 30.degree.. The square is commonly made of a plastic material or metal.
Numerous proposals have been made to render set squares more versatile. However none of these seems to have had any success. This is probably because they either add little to the potential utility of the square, or because they are so complicated as to frighten off potential users and/or to increase manufacturing costs substantially.
For example, U.S. Pat. No. 2,043,729 (Bilder) discloses a 90.degree./45.degree./45.degree. set square having three cut-outs which provide various straight edges at predetermined angles to external edges. There are also numerous apertures for use in drawing circles, and a protractor scale. The whole is of dauntingly complicated appearance, and would apparently require much practice to master. U.S. Pat. No. 1,598,690 (Petronio) discloses a 90.degree./60.degree./30.degree. set square with three apertures (a slot and two triangles) for providing further angles. The triangles are right-angled, with the perpendicular sides parallel to those of the set-square. Thus only the hypotenuses provide additional angles. Generally, a given angle is obtainable only relative to one particular external side. Thus the user must locate the square the correct way up, and select the correct aperture. There is also a protractor scale, symmetrical about the 90.degree. angle of the square, its origin indicated by an aperture.
Further examples of patent specifications disclosing modified set-squares are:
French No. 908163 (Vardanian) PA1 French No. 934943 (Le Material Automatique Electrique) PA1 French No. 957869 (Lewin) PA1 French No. 981857 (Cordani) PA1 French No. 1124247 (Balloche) PA1 French No. 1208614 (Hoellinger) PA1 French No. 2351801 (Bord) PA1 U.S. Pat. No. 1,845,449 (Smith) PA1 U.S. Pat. No. 3,375,589 (Dolgorukov) PA1 Swiss No. 276736 (Clerc) PA1 G.B. No. 794192 (Midulla)